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Abstract
The present work compared between the Egyptian and imported polypropylene films. Four types of Egyptian and corresponding imported polypropylene films were collected and characterized according to their physical, mechanical, optical properties and print quality.
This work also aimed to study the effect of the atmospheric pressure dielectric barrier discharge (APDBD) plasma treatment on the chemical structure and morphology of the surface of transparent BOPP film using UV-visible, FT-IR, SEM and AFM techniques.
Print quality of polypropylene films was evaluated by measuring print gloss, print density and print adhesion
It was found that the Egyptian polypropylene films were more wettable and ink receptive than the imported films. Egyptian films were stronger, had the ability to absorb and dissipate mechanical shock and had lower problems in print registration than the imported films. Egyptian films were glossier, clearer, more transparent and homogeneous, and had the most consumer appeal, than the corresponding imported films. The high coefficient of friction (COF) of the Egyptian polypropylene films may result in some problems such as deformation of the film, web breaks, wear of machine parts and fire hazard. The COF of Egyptian films can be reduced by increasing of the amount of slip additives incorporated into the resin.
The SEM and AFM results showed that the surface of untreated transparent BOPP film seemed to be smooth and flat. However, after atmospheric plasma treatment, formation of protrusions and increasing of surface roughness appeared. Surface roughening offers stronger molecular sites for interaction between the printing ink and the polypropylene sample. Atmospheric plasma treatment increased the concentration of the carbonyl and vinylic bonds at the surface.
It was observed that the surface energy of the treated film increased as the treatment time increased. The surface energy of atmospheric plasma treated film decreased from 68 dyne/cm, through 45 hours, to 64 dyne/cm. It settled at that level for further storage.
The results showed that the untreated transparent BOPP film exhibited failure in ink adhesion, however the atmospheric plasma treated films displayed excellent ink adhesion. It was observed that there was an increase of print density and a decrease of print gloss with increasing of treatment time, at low ink film thickness. SEM micrographs showed that the contour of ink cells of printed treated film had more regular cell structures than that in case of printed untreated film. As a result, the treated film had a higher print density value than the untreated film. Since print gloss affected by surface roughness of the substrate, print gloss of atmospheric plasma treated film was found to be less than that of untreated one at low ink film thickness.